Dear friends. I am working on a project where an arduino uno and a GPS receiver are involved. The gps unit transmitts serial data NMEA. The data string on Hyperterminal looks like this : $GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47 $GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39 $GPGSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45*75 Here is a link that explains in detail what the above strings are about: https://www.gpsinformation.org/dale/nmea.htm what i want the arduino to do is read the below string (sentence) and ignore the rest. $GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39 With picaxe, i was able to do this by using these bits ( GSA ) as a qualifier and store all rest bits for later calculations ,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39 Also i need the serial to "timeout" if this ( GSA ) string is not transmitted for a period longer than 1 second. The reason for the above is that first i only need the GSA sentence while i dont want my Microcontroller to "hang" waiting to receive this sentence (or any other) if the GPS unit is not connected. I am open to ideas Thank you.